The present invention relates to the field of optical amplifiers and, more particularly, to a method and apparatus for holding optical fiber transports.
Submarine fiber optic communication systems carry a large majority of the information that is transmitted between the world""s continents. These fiber optic communication systems remain in-place on the bottom of the ocean under thousands of feet, and even miles, of water for years at a time. Due to the difficulties encountered when having to repair, replace, or generally service these systems, it is desirable that these systems be highly reliable.
Submarine fiber optic communication systems typically include repeaters that appear at regular intervals along the spans of undersea cables to amplify the optical signals traversing the constituent fibers. Other assemblies that may be found along a submarine communication system include branching units, which allow multiple cable stations to be served from a single cable. To protect the sensitive components and/or connections that are housed within these submerged assemblies, a rugged hermetically sealed structure must be employed.
Typically, the optical fibers found within optical repeaters are circular in cross-section, and are constructed of glass surrounded by a protective jacket that is thicker than the glass. For example, a typical glass fiber (xe2x80x9cglass fiberxe2x80x9d, xe2x80x9cbare fiberxe2x80x9d, or xe2x80x9cunjacketed fiberxe2x80x9d) can have an outer diameter of approximately 0.010 inches, and a typical jacketed fiber can have an outer diameter of approximately 0.040 to 0.060 inches.
The glass fiber is fragile. Because even microscopic damage to the glass fiber can adversely affect the reliability of the optical repeater (and, as a result, the reliability of the entire submarine optical fiber cable system), great efforts are normally taken to protect the glass fiber from damage. Generally, the likelihood of damage to the glass fiber can be reduced by ensuring that any curvature in the glass fiber meets or exceeds the minimum bending radius of the glass fiber. However, the minimum bending radius of the glass fiber is a function of the expected life of the glass fiber. For example, when at least a 25-year life is expected, the glass fiber typically has a minimum bending radius of approximately 1 inch. This is referred to as the reliability-adjusted minimum bending radius of the glass fiber, because meeting or exceeding this value provides acceptable reliability from bending damage during the expected life of the glass fiber.
Typically, the optical components found within optical repeaters are manufactured with a segment of optical fiber attached at each end and cut to a specified length. Each fiber segment contains a jacketed portion of specified length located adjacent to the optical component, and a bare portion of specified length extending from the opposite end of the jacketed portion. The bare portion is spliced into the bare portion of another segment in the repeater""s optical circuit. Creating these splices can be a complicated task, requiring substantial lengths of bare fiber on each side of the splice.
Optimally however, the repeater or branching station is designed to be as space-efficient as possible, thereby minimizing its production, storage, shipping, and installation costs. Thus, it is desirable to store each optical fiber segment in the most space-efficient manner possible.
Typically, this involves storing the fiber in a coiled configuration on a tray upon which are mounted at least some of the optical components served by that fiber. Typical trays include a well that extends partially through the thickness of the tray, and an elongated circular spool surrounded by the well. A gap between the spool and the well defines a fiber storage space within which the coiled fibers can rest.
An improvement in this storage approach is described in the United States Patent Application titled xe2x80x9cDevice for Separating Portions of Spooled Optical Fibersxe2x80x9d, application Ser. No. 09/317,827, filed May 25, 1999, which is incorporated herein by reference. This improved storage approach was developed at least partially in response to the design requirements of a new repeater, which was designed to provide repeater services for a substantially increased number of optical fiber communication connections. The new repeater has a substantially different physical architecture than the earlier model repeaters. The new repeater employs a plurality of optical amplifier pairs (xe2x80x9camp-pairsxe2x80x9d) that amplify the signal on a full duplex optical fiber communication connection, which is also known as a fiber pair. Each amp-pair includes a plurality of optical component trays containing optical components connected by optical fibers that are stored in a fiber storage space on that tray. In addition, each optical component tray has at least two optical fibers associated therewith.
During assembly, the optical fibers of the optical component trays can be connected by splices to form a working optical amplifier. Because an amp-pair may be moved through several stations during the assembly process, there is a need for protecting the optical fibers during the transport. For example, optical fibers could be damaged if they come into contact with sharp objects that may scratch the surface of the fiber. Such damage, while possibly not readily apparent, could reduce the working life of the optical fiber substantially and result in a faulty optical amplifier. Therefore, there is a need for protecting the optical fibers during transport from one assembly station to another.
In addition, once a given amp pair is assembled and its optical fibers have been interconnected, a need can arise to test the optical performance of that amp pair. Such testing can require accessing the ends of one or more fibers from a fiber storage space of the amp pair. Frequently, the fiber of interest is not the outer-most fiber in the storage space, but is instead located beneath other optical fibers. In this situation, the outer-most fibers must be temporarily removed from the storage space and set aside until activities involving the fiber of interest are completed.
Typically, this is accomplished by coiling each fiber around an optical fiber transport, and stacking the optical fiber transports together on a common pin. This creates a problem, however, because each fiber can not be independently accessed. Instead, to access a fiber coiled about a transport that is low in the stack, the upper transports must be temporarily removed from the common pin. Each movement of a transport, however, increases the risk of damage to the fiber coiled on and extending from that transport. Therefore, there is a need for a device and method for temporarily storing the optical fibers normally stored in the fiber storage space of the tray such that each fiber remains independently accessible.
An embodiment of the present invention provides a method for interconnecting at least one pair of optical fibers attached to an amp pair, the method including storing each of the optical fibers on a fiber transport attached to the amp pair, placing the amp pair into a splicing station, moving the fiber transports, splicing at least two of the optical fibers; and receiving fiber transports on a holder attached to the amp pair.
According to one embodiment of the invention, a device for storing and transporting fiber transports includes a plurality of storage slots that removably hold the fiber transports.
Other embodiments of the present invention provide a device for holding a plurality of optical fiber transports associated with an optical fiber storage assembly. The device includes a fixture adapted to mount to the optical fiber storage assembly. The fixture is also adapted to separately receive each optical fiber transport from the plurality of optical fiber transports.